Abstract : The formalism for a complete treatment of elastic wave scattering from cylindrical cavities and solid inclusions has been worked out for both perpendicular and oblique indice. Special cases, e.g., fluid cylinders enclosed in fluid or solid media, have already been numerically analyzed. Poles of scattering amplitudes in the complex frequency plane have been found, and were physically interpreted in terms of helical surface waves on the cylinders propagating in both the interior and the exterior medium. Dispersion, attenuation and refraction of these surface waves have been obtained. (Author)